I'm not a plumber, but...
The upstairs bathroom had sprung a leak from the tiled shower space, and a quick-fix coat the tiles with some kind of stuff was called in to fix it, by painting gunk over the tiles. Guess what - the quick fix didn't fix it. The tiles were ripped out in a full bathroom reno, a plastic shower base was installed, and (you can't skip the waterproofing) the walls were waterproofed and tiles. No leaks. Note: the plastic shower base now has scratches on it or some reason. People walking in there with shoes on. Don't know. Make sure you get a good quality base. Also, the plumber on my reno had trouble with the plumbing. The drain went too far down and threatened to foul the ceiling below. Watch him, and make sure there is sufficient clearance for the drain pipe.